The overall objective of the proposed research is to gain insight into the mechanisms by which cariogenic bacteria such as Streptococcus mutans can synergistically and antagonistically interact with other plaque bacteria during dental plaque formation. The specific objectives are: (1) to utilize our quantitative in vitro plaque forming assay to analyze factors involved in heterotypic interactions between oral bacteria; (2) to analyze the interaction and association of the S. mutans dextransucrase with lipids in order to evaluate the role of such molecules in glucan production and adherence; and (3) to continue evaluation of the association between dextranase-producing oral bacteria and S. mutans. The long-term goal is to define interactions involved in regulating the microbial content of plaque which could be used to develop caries control measures based on selective inhibition of specific cariogenic bacteria.